Holographic lens and liquid crystal image source for head-up display

• US 3,915,548 A
• Filed: 11/29/1974
• Issued: 10/28/1975
• Est. Priority Date: 04/30/1973
• Status: Expired due to Term

• Current Assignee: Donald H. Close, Eugene W. Opittek, Michael N. Ernstoff, Richard N. Winner, William C. Hoffman
• Original Assignee: Donald H. Close, Eugene W. Opittek, Michael N. Ernstoff, Richard N. Winner, William C. Hoffman
• Inventors: Opittek, Eugene W., Hoffman, William C., Ernstoff, Michael N., Close, Donald H., Winner, Richard N.
• Primary Examiner(s): Stern, Ronald J.
• Application Number:
  US05/528,198
• Time in Patent Office: 333 Days
• Field of Search: 350/3.5,162SF,16LC,174 35/12N
• US Class Current: 345/7
• CPC Class Codes: G02B 2027/0107 with optical power
• CPC Class Codes: G02B 2027/0109 comprising details concerning the making of holograms
• CPC Class Codes: G02B 2027/0118 comprising devices for improving the contrast of the display / brillance control visibility
• CPC Class Codes: G02B 2027/0129 comprising devices for correcting parallax
• CPC Class Codes: G02B 2027/0145 creating an intermediate image
• CPC Class Codes: G02B 2027/0165 associated with a head-down display
• CPC Class Codes: G02B 27/01 Head-up displays
• CPC Class Codes: G02B 27/0103 comprising holographic elements
• CPC Class Codes: G02F 1/136277 formed on a semiconductor substrate, e.g. of silicon

Abstract

A head-up display system is disclosed for use in aircraft to display symbols and sensor video. The system uses an array of holographic elements on a transparent plate, or on the inside of the aircraft canopy, as both a collimating lens and a combiner for a light image from a liquid crystal source. An optimum system employs a holographic combiner/lens and a liquid crystal image source, but a holographic combiner/lens may be used with other image sources, and a liquid crystal image source may be used with other collimating lens and combiner arrangements. The thin and flat liquid crystal image source permits its use in an optimum position in the cockpit for both head-up and head-down viewing.

Claims

1. In an aircraft, a head-up display system for use in displaying an image for viewing by a pilot in the pilot'"'"''"'"'s field of view while looking out of the aircraft at a scene in a forward direction, comprising in combination:

an aircraft canopy integral with the aircraft;

a holographic lens comprising an optically transparent substrate having photoresponsive material having as an integral portion thereof a plurality of holographic elements in a side-by-side abutting arrangement for collimating light from a focal plane, and having a known operating bandwidth of light of preselected wavelengths, said lens being disposed in said aircraft in the field of view for collimating light directed to the pilot from all points of a light image produced in the focal plane and simultaneously combining the image light thus collimated and directed to the pilot with light from said scene whereby said pilot sees said image as if emanating from a source in said field of view at infinity, said holographic lens being disposed on the inside surface of said canopy;

a relay lens; and

means optically coupled to the holographic lens for producing said light image at said focal plane, said image having a peak band of wavelengths within the operating bandwidth of said holographic lens, and wherein said means for producing said light image at said focal plane is comprised of;

an array of liquid crystal cells disposed in rows and columns in an image source plane, said relay lens projecting said image source plane to said focal plane, each cell of said array of liquid crystal cells comprising conductive plates parallel to said focal plane and a layer of liquid crystal material sandwiched in the mesophase state;

an array of horizontal and vertical transparent conductors, each one of said horizontal conductors being connected to all cell plates on one side of said array of cells of a distinct one of said rows of cells, and each one of said vertical conductors being connected to all cell plates on another side of said array of cells of a distinct one of said columns of cells;

means electrically connected to said transparent conductors, for selectively energizing said distinct one of each of the rows and columns of the conductors energized at one time to establish an electric field across said layer of liquid crystal between the plates of a single cell; and

a light source so disposed as to illuminate said holographic lens through said array of cells and said relay lens, said source emitting light having said peak band of wavelengths, whereby light incident on said holographic lens is modulated at different points to produce said light image as a function of electric fields established across said cells.

2. The combination of claim 1 wherein said light source is disposed on the same side of saiD array of cells as said holographic lens and the conductive plate of each cell on the side of the array facing said light source is transparent while the other conductive plate of each cell is reflective to provide a liquid crystal image source operating in the reflective mode.

3. The combination of claim 2 wherein said light source is a point source and a collimating lens between said point source and said array of cells.

4. The combination of claim 3 wherein said holographic lens is formed for collimating light from a focal plane by recording interference patterns on a transparent film of recording medium, said patterns being formed by coherent light from said focal plane, and coherent light from a surface virtually at infinity, said light from said focal plane being everywhere coherent with light from said surface while recording, whereby light from points on said image means produced in said focal plane and incident on said recording medium after said holographic lens has been formed reconstructs collimated light from corresponding points on said surface virtually at infinity, thereby reconstructing said image with collimated light directed from said record medium to said pilot in the same direction as light from outside said aircraft in said field of view.

5. The combination of claim 4 wherein said interference patterns are recorded with light from said focal plane on said recording medium on a side opposite light from said surface virtually at infinity, and said holographic lens is disposed in said aircraft with said focal plane on the same side of said record medium as a seat for said pilot to provide a reflection-type holographic lens which also functions as a combiner.

6. The combination of claim 1 wherein said light source is disposed on the opposite side of said array of cells as said holographic lens and the conductive plates on both sides of said cells are transparent to provide a liquid crystal image source operating in a transmissive mode.

7. The combination of claim 6 wherein said light source is a diffused area source.

8. The combination of claim 6 wherein said holographic lens is formed for collimating light from a focal plane by recording interference patterns on a transparent film of recording medium, said patterns being formed by coherent light from said focal plane, and coherent light from a surface virtually at infinity, said light from said focal plane being everywhere coherent with light from said surface while recording, whereby light from points on said image means produced in said focal plane and incident on said recording medium after said holographic lens has been formed reconstructs collimated light from corresponding points on said surface virtually at infinity, thereby reconstructing said image with collimated light directed from said record medium to said pilot in the same direction as light from outside said aircraft in said field of view.

9. The combination of claim 8 wherein said intereference patterns are recorded with light from said focal plane on the same side of said recording medium as light from said source virtually at infinity, and said holographic lens is disposed in said aircraft with said focal plane on the opposite side of said recording medium as a seat for said pilot to provide a transmission-type holographic lens which also functions as a combiner.